Brake anti-lock mechanism

ABSTRACT

An electro-pneumatic control valve for use in a brake anti-lock system is provided with a relay portion for controlling fluid pressure applied to the system in response to predeterminately selected fluid pressure samples supplied thereto and electric sampling means responsive to signals supplied thereto upon the occur-rence of pre-selected conditions in the brake system for controlling the fluid pressure samples supplied to said relay portion.

United States Patent 1 1 Machek I Sept.1l, 1973 [5 BRAKE ANTI-LOCKMECHANISM 3,677,610 7/1972 Pauwcls 61 al 303 21 F [75] Inventor: John A.Machek, Creve Coeur, Mo.

Primary ExaminerDuane Reger [73] Ass1gnee: Wagner Electric Corporation,Auomey joseph papin Newark, N.J.

FllCdZ Jan. 17, 1972 57 ABSTRACT PP 2181293 An electro-pneumatic controlvalvefor use in a brake anti-lock system is provided with a relayportion for 1521 Us. 01 303/40,'303/21 F controlling fluid Pressureapplied to the System in [51 1111. c1 .Q B60t 8/12 SPOnse toPredeterminately Selected fluid Pressure [58] Field of Search 137/596,596.16; P Supplied thereto and electric Sampling means 1 8 1 1 303/21 F2 CG, 29 40 sponsive to signals supplied thereto upon the occurv renceof pre-selected conditions in the brake system for 5 References Citedcontrolling the fluid pressure samples supplied to said UNITED STATESPATENTS 2/1962 39 Claims, 2 Drawing Figures Dobrikin 303/40 BRAKEANTI-LOCK MECHANISM FIELD OF THE INVENTION This invention relatesgenerally to brake anti-lock systems and in particular to anelectro-pneumatic control valve for use in such systems.

BACKGROUND OF THE INVENTION In past brake anti-lock systems, varioustypes of control valves were utilized to control the application offluid pressure from a source thereof to at least some of the vehiclebrakes of said brake system; however, one of the main undesirable ordisadvantageous features of such past control valves was that theytended to overshoot in applying the pressure to the brake therebydriving the braked wheel to a locked condition. Another undesirable ordisadvantageous feature of such past control valves was that suchovershooting of the desired braking pressure which locked the vehiclewheel resulted in loss of vehicle steering stability and confused thesystem logic or electronics since the logic has difficulty indistinguishing between a stopped vehicle wheel and a locked vehiclewheel. Still another disadvantageous or undesirable feature of such pastcontrol valves was that they consumed or exhausted too much systempressure which burdened the make-up capabilities thereof. And yetanother disadvantageous or undesirable feature of such past controlvalves was that they compared the instantaneous system pressure onlywith that which was applied immediately prior thereto.

The principle object of the present invention is to provide a controlvalve for a brake anti-lock system which overcomes the aforementioneddisadvantageous or undesirable features of the past control valves, andthis, as well as other objects and advantageous features of the presentinvention, will become apparent in the specification which follows.

SUMMARY OF THE INVENTION Briefly, the present invention includes acontrol valve for a brake anti-lock system having relay means effectingthe application to said system of supplied fluid pres- BRIEF DESCRIPTIONOF THE DRAWINGS In the drawings, which illustrate embodiments of theinvention and wherein like numerals refer to like parts wherever theyoccur:

FIG. 1 is a sectional view showing a control valve embodying the presentinvention in cross-section; and

FIG. 2 is a partial sectional view illustrating another control valveembodying the present invention in crosssection. I

Referring now to the drawing in detail, an anti-lock device or controlvalve 1 for a brake anti-lock system (not shown) is provided with ahousing 2 having upper, intermediate and lower portions 3, 4, 5 whichare interconnected by suitable means, such as the studs 6, and seals orO-ring members 7, 8 are sealably interposed between said upper andintermediate housing portions and said intermediate and lower housingportions, respectively.

The lower housing 5 is provided with a bore 9 interposed between opposedcounterbores 10, 11, said counterbore l0 defining an inlet chamber, andopposed annular shoulders l2, 13 are provided on said housing at theintersections of said bore with said counterbores, respectively, saidshoulder 12 defining a valve seat. An inlet port 14, which is adaptedfor connection with a fluid pressure source (not shown), is provided inthe lower housing 5 intersecting with the counterbore l0, and an outletport 15, which is adapted for connection with a vehicle brake (notshown), is also provided in said lower housing intersecting with theshoulder 13. A valve guide member 16 having a bore 17 therethrough ispositioned in the lower end of the counterbore 10 against displacementby a groove and snap ring assembly 18, and a valve member 19 is slidablyreceived in the guide bore 17 having a sealing head or portion 20 urgedinto sealing engagement with the valve seat l2 by the negligible forceof a valve spring 21 interposed between said valve member and said guideisolating the inlet chamber 10. A bore or exhaust passage 22 is providedthrough the valve member 19 normally connecting the counterbore 11 tothe atmosphere, and seals 23, 24 are carried in the guide member 16 insealing engagement with the lower end of the counterbore l0 and saidvalve member, respectively. A relay member or piston 25 having opposedsides or faces 26, 27 is slidably received in the counterbore 11carrying a peripheral seal or O-ring 28 in sealing engagement with saidcounterbore. An extension 29 is integrally formed with the piston 25 onthe lower side 26 thereof having a free end portion 30 which defines avalve seat for engagement with the valve member 19 about the exhaustpassage 22 thereof, as discussed hereinafter, and a return spring 31 isinterposed between the relay piston side 26 and the housing shoulder 13normally maintaining said valve seat 30 displaced from said valve memberand urging the relay piston upper side 27 into abutment with the lowerend or shoulder 32 of the intermediate housing 4 which closes thecounterbore 11. The intermediate housing 4 is provided with a centrallylocated guide recess 33 therein which slidably and guidably receivesanother extension or guide 34 integrally formed with the relay pistonupper side 27, and an expansible control or sampling chamber 35 isdefined in the counterbore 11 between said relay piston upper face andsaid intermediate housing lower end in opposition to an outlet chamber36 also defined in said counterbore between the relay piston lower face26 and the housing shoulder 13.

The intermediate housing 4 is provided with companion solenoid chambersor bores 37, 37a intersecting with the upper end 38 of said intermediatehousing and having base or end walls 39, 39a, and a wall 40 which isintegral with said intermediate housing is provided between saidsolenoid chambers being cross-slotted at 41 to define a lead-out passagefor the terminals 42, 42a of solenoids 43, 43a, as discussedhereinafter. A control or sampling port 44, which is adapted forconnection with an operator controlled service foot or application valveof the brake system (not shown), is provided in the intermediate housing4 intersecting with the larger of stepped vertical bores 45, 46, andsaid stepped bores intersect with the bore end wall 39 and intermediatehousing lower end 32,, respectively. An insert 47 is threadedly receivedin the lower end of the larger stepped bore 45 having a passage 48therethrough connecting between the sampling chamber 35 and inlet port44, and a valve seat 49 is provided on said insert about said passagefor engagement with a uni-directional valve member or check valve 50which is normally urged thereinto by the negligible force of a valvespring 51 biased between said check valve and the intermediate housing4.

Solenoids 43, 43a are provided with pole pieces 52, 52a which extendcoaxially into the solenoid chambers 37, 37a, and the pole piece 52 isseated in abutting engagement with the solenoid chamber end wall 39extending into the smaller stepped bore 46 in supporting and guidingengagement therewith while th pole piece 520 is seated in abuttingengagement with the solenoid chamber end wall 39a and extends into arecess 53 provided in the intermediate housing 4 in supporting andguiding engagement therewith. Annular cylindrical electrical coils 54,54a of the solenoids 43, 43a are positioned in the solenoid chambers 37,37a and supported on the pole pieces 52, 52a, and the terminal or leads42, 42a of said coils are lead out of the intermediate housing 4 throughthe lead-out slots 41 for connection with the logic or electronicportion of the brake anti-lock system (not shown). Tubular or sleevemembers 55, 55a having bores 56, 56a therethrough extend coaxiallythrough the coils 54, 54a in sealing engagement with seals 57, 57a and58, 58a respectively carried in the pole pieces 52, 52a and coilretainers 59, 59a which are retained in displacement preventingengagement with the upper end of said coils by a clip spring 60 biasedbetween the housing cover 3 and said retainers.

Hexagonally shaped armature members 61, 61a of the solenoids 43, 43a arereciprocally received in the sleeve member bores 56, 56a having exhaustvalve members 62, 62a in the upper ends thereof normally urged intosealing engagement with exhaust valve seats 63, 63a provided on thecover housing 3 about exhaust passages 64, 64a therein by the negligibleforce of return springs 65, 65a biased between said armature members andthe retainers, respectively. In the preferred embodiment, it should benoted that the exhaust passage 64 is appreciably smaller than theexhaust passage 64a to restrict the relative rates of exhausting fluidpressure flow, as discussed hereinafter; however, it is apparent thatexhaust passages 64, 64a can be of substantially equal size, if desired.The relative sizes of the exhaust passages 64, 64a depend, or arecorrelated with, the volumetric characteristics of the brake system (notshown), and if the volume of the brake system is relatively small, theexhaust passage 64 can be omitted, as shown in FIG. 2. Another valvemember 66 is carried in the lower end of the armature 61 and normallydisplaced from sealing engagement with a valve seat 67 provided on theupper end of the pole piece 52 about a passage or bore 68 therethroughconnecting the 4 larger stepped bore 45 with the sleeve member bore 56.

To complete the description of the control valve 1, another passage 69is provided in the intermediate housing 4 connected between the samplingchamber 35 and the solenoid chambers 37, 37a above the retainers 59, 59atherein, and it is apparent that a restricted or tortuous flow passagemeans, indicated generally at B, is defined between the inlet port 44and said sampling chambers by the larger stepped bore 45, the pole piecepassage 68, the sleeve member bore 56, the portions of the solenoidchambers 37, 37a above the retainers 59,

59a therein, and the passage 69; however, while the restriction of theflow passage B is provided between the various components defining such,it is contemplated that said flow passage can also be restricted byvarious permanent or adjustable flow throttling or restricting devicessuch as orifices, vortexes, needle valves, or the like which are wellknown in the art.

OPERATION With the component parts of the control valve 1 positioned asshown in the drawing and as described, if the vehicle operator desiresto effect a service brake application or brake energization todecelerate the vehicle, a control or sampling fluid pressure is suppliedto the control port 44 upon operator actuation of an application or footvalve of a type well known in the art (not shown). The control fluidpressure flows from the control port 44 through the flow passage B tothe control chamber 35 acting on the effective area of the relay piston25 therein to create a control force Fc urging said relay pistondownwardly against its return spring 31. This downward movementinitially engages the relay piston valve seat 30 with the valve member19 closing the exhaust passage 22 thereof andisolating the outletchamber 36 from the atmosphere, and said downward movement thereafterurges said valve member against its valve spring 21 to a positiondisengaged from the housing valve seat 12 to establish pressure fluidcommunication between the inlet and outlet ports 14, 15. Supplied orinput fluid pressure flows from its source (not shown) through the inletport 14, the inlet chamber 10, the outlet chamber 36 to establish anoutput or applied fluid pressure at the outlet port 15 which is, ofcourse, effective to energize the vehicle brakes (not shown) connectedtherewith and decelerate the vehicle.

When the reaction force Fr created by the established output fluidpressure in the output chamber 36 acting on the effective area of therelay piston 25 therein substantially equals the control force Fc, saidrelay piston is moved upwardly toward a lapped position, and said valvemember follows toward the lapped position in lapped engagement betweenthe relay piston valve seat 30 and the housing valve seat 12. If agreater braking application is desired to increase the intensity ofbrake energization and vehicle deceleration, the magnitude of thecontrol fluid pressure is increased which results in an increasedcontrol force F0 to further actuate the relay piston 25 and valve member19, as previously described, toward their lapped positions effecting acorresponding increase in the magnitude of the output fluid pressure.

[f the desired braking effort or brake energization is attained withoutengendering a wheel lock-up or vehicle skid condition and the operatorde-actuates the foot valve to exhaust the control fluid pressure at thecontrol port 44 to the atmosphere, a fluid pressure differential is, ofcourse, established across the unidirectional valve 50 between thecontrol fluid pressure in the control chamber 35 and that exhausting toatmosphere through the control port 44, and said uni-directional valveis movable against its return spring 51 in response to said fluidpressure differential acting thereacross toward a position displacedfrom the insert valve seat 49 to open the insert passage 48 therebyeffecting the exhausting flow of the control fluid pressure from thecontrol chamber 35 through said insert passage and the housing largerstepped bore 45 directly to said control port which, in effect,short-circuits or by-passes the restricted flow passage means B toeffect very rapid exhaustion of the control fluid pressure from thecontrol chamber 35, the reaction force Fr and the return spring 31 urgesthe relay piston upwardly toward its original position in engagementwith the intermediate housing abutment 27 disengaging the valve seat 30from the valve member 19 to again open the valve member exhaust passage22 reestablishing exhausting communication between the outlet port andchamber 15, 36 and the atmosphere. In this manner, the output fluidpressure is exhausted from the brakes to effect deenergization thereofthrough the outlet port and chamber 15, 36 and the valve member exhaustpassage 22 to the atmosphere, and upon such exhaustion of the outputfluid pressure, the reaction force Fr is, of course, eliminated.

If the output fluid pressure applied to energize the vehicle brakesduring the above-described brake applica tion is of a magnitude greatenough to effect a wheel lock-up or vehicle skid condition, the brakeanti-lock system logic and sensor portions (not shown) ascertains suchwheel lock-up and signals the control valve 1 indicating, in effect,that the magnitude of the output fluid pressure should be reduced. Thelogic signal excites or energizes the coil 54 of the solenoid 43creating a magnetic force which moves the armature 61 downwardly againstits return spring 65 into magnetic holding engagement with the polepiece 52, and in this manner, the armature valve member 66 is engagedwith the pole piece valve seat 67 to close the pole piece passage 68isolating the control port 44 while the armature exhaust valve member 62is disengaged from the upper housing exhaust valve seat 63 to open therestricted exhaust passage 64. With the control port 44 isolated and theexhaust passage 64 so opened, a restricted exhausting flow of controlfluid pressure is effected from the control chamber through the passage69, the portion of the solenoid chambers 37, 37a above the solenoidretainers 59, 59a, and the open exhaust passage 64 to the atmospherethereby rather slowly reducing the magnitude of the control fluid insaid control chamber to correspondingly reduce the magnitude of thecontrol force Fc. Since the control fluid pressure is being exhausted toeffect a continuous reduction of the control force Fc, the reactionforce Fr urges the relay piston 25 upwardly from its lapped position todisplace the valve seat 30 thereof from the valve member 19 therebyopening the valve member exhaust passage 22 and exhausting the outputfluid pressure from the vehicle brakes to the atmosphere. Of course, itis apparent that such restricted exhausting flow of the control fluidpressure from the control chamber 35 effects a corresponding reductionof the output fluid pressure applied at the outlet port 15 and to thevehicle brake to also effect a corresponding reduction of the intensityof the brake energization.

If the aforementioned reduction of the intensity 0 the brakeenergization does not alleviate the wheel lock-up or vehicle skidcondition, the sensor and logic portions of the brake system discernsuch and again signal the control valve 1 that such wheel lock-up iscontinuing indicating, in effect, that the output fluid pressure shouldbe further reduced. This additional logic signal energizes the coil 54aof the solenoid 43a creating a magnetic force which moves the armature61a downwardly against th return spring 65a into magnetic holdingengagement with the pole piece 52a, and in this manner, the armaturevalve member 62a is displaced from the upper housing exhaust valve seat63a to also open the exhaust passage 64a. With both the exhaust passages64, 64a open and the control port 44 isolated, it is apparent that thecontrol fluid pressure is now exhausted from the control chamber 35 at amore rapid rate providing a more rapid exhaustion of the outlet fluidpressure in the same manner as discussed hereinbefore which, of course,effects a corresponding reduction of the intensity of the energizationof the vehicle brakes and a rather rapid alleviation of the wheellock-up or skid condition.

When the sensor and logic portions of the brake system determine thatthe wheel lock-up condition has been alleviated, the signals to thesolenoids 43, 43a of the control valve 1 are terminated whichde-energizes the solenoid coils 54, 54a and elmininates the attractivemagnetic force between the pole pieces 52, 52a and armatures 61, 61a,respectively. Upon the elimination of the magnetic force, the returnsprings 65, 65a move the armatures 61, 61a upwardly toward theiroriginal positions re-engagingthe exhaust valve members 62, 62a with theupper housing valve seats 63, 63a closing the exhaust passages 64, 64a,respectively, and of course, the movement of the armature 61 to itsoriginal position also disengages the valve member 66 thereof from thepole piece valve seat 67 to open the pole piece passage 68 andre-establish pressure fluid communication through the flow passage Bbetween the control port 44 and the control chamber 35.

When communication between the controlport 44 and the control chamber 35is re-established, the relay piston 25 and valve member 19 are againactuated to increase the magnitude of the output fluid pressure appliedto the outlet port 15 and the vehicle brakes to effect a correspondingincrease in the energization thereof, and if such increased brakeenergization again effects a wheel lock-up condition, the brakeanti-lock system re-cycles wherein the sensor. and logic portionsthereof again signal the control valve 1 to reduce the output fluidpressure in the same manner as previously described. Of course, thebrake anti-lock system and control valve 1 continue such re-cycling toalleviate the occurrence of wheel lock-up conditions until the desiredvehicle deceleration is attained.

Referring now to FIG. 2, another anti-lock device or control is shownfunctioning in substantially the same manner and having substantiallythe same component parts, as the previously described control valve 1with the exception that only the exhaust passage 64a is provided in theupper housing 103 of the control valve 100 since, as previouslymentioned, the control valve 100 is contemplated for use in anti-lockbrake systems having a comparatively small volumetric capacity.

In the operation of the control valve 100, the relay piston 25 isactuated in response to control fluid pressure applied to the controlport and chamber 44, 35 to effect a corresponding output fluid pressureat the outlet port 15 for energizing the vehicle brakes, and if suchbrake energization results in a wheel lock-up condition, the sensor andlogic portion effects a signal to energize the solenoid 43 and move thearmature valve member 66 into engagement with the pole piece valve seat67 closing the passage 68 to isolate said control port, as previouslydescribed. If the wheel lock-up continues,

the sensor and logic portion effects the additional signal to energizethe solenoid 43a and move the armature 61a into magnetic holdingengagement with the pole piece 52a displacing the armature valve member62a from the upper housing exhaust valve seat 63a to open the exhaustpassage 64a, and the exhausting flow of control fluid pressure isthereby effected at a rather rapid rate from the control chamber 35through the passage 69 and the open exhaust passage 64a to theatmosphere. When the control force Fe is so reduced, the reaction forceFr urges the relay piston 25 upwardly from its lapped position todisengage the valve seat 30 thereof from the valve member 19 to open itsexhaust passage 22 and exhaust to the atmosphere the output fluidpressure applied to the brakes to reduce the intensity of theenergization thereof. Upon alleviation of the wheel lock-up condition inresponse to the reduction of the intensity of the brake energization,the logic and sensor portions terminate the signals to the control valve100 de-energizing the solenoids 43, 43a, and the armature return springs65, 65a return the armatures 61, 61a to their original positionsre-establishing pressure fluid communication between the control portand chamber 44, 35 through the flow passage B and reengaging the valvemember 62a with its valve seat 630 to close the exhaust passage 64a.

When pressure fluid communication is re-established between the controlport and chamber 44, 35, the control force Fc again actuates the relaypiston 25 and valve member 19 to re-establish or increase the outputfluid pressure applied to the outlet port and the vehicle brake toeffect a corresponding increase in the energization thereof, and if suchbrake energization again results in a wheel lock-up condition, the brakeantilock system recycles wherein the sensor and logic portions againsignal the control valve 100 to reduce the output fluid pressure, aspreviously described. Of course, the brake anti-lock system and controlvalve 104 continues such re-cycling to alleviate the occurrence of wheellock-up conditions until the desired vehicle deceleration is attained.

From the foregoing, it is now apparent that novel anti-lock devices 1,100 meeting the objects and advantageous features set forthhereinbefore, as well as others, are provided and that changes as to theprecise configurations, shapes and details of the constructions setforth in the disclosure by way of illustration may be made by thoseskilled in the art without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A control valve for an anti-lock brake system com-, prising ahousing, relay means movable in said housing and operable generally inresponse to control fluid pressure subjected thereto to effect a meteredapplication through said housing of fluid pressure supplied thereto, andmeans for controlling the control fluid pressure subjected to said relaymeans comprising an electric solenoid valve energized in response to apreselected condition to isolate the control fluid pressure acting onsaid relay means and vent the isolated control fluid pressure, saidrelay means being responsive to the reduction of the control fluidpressure upon the venting thereof to effect a proportional reduction ofthe applied fluid pressure.

2. A control valve for an anti-lock brake system comprising a housing,relay means movable in said housing and operable generally in responseto control fluid pressure subjected thereto to effect a meteredapplication through said housing of fluid pressure supplied thereto, andmeans for controlling the control fluid pressure subjected to said relaymeans comprising a first electric solenoid means energized in responseto a preselected condition to isolate the control fluid pressure actingon said relay means, and a second electric solenoid means energized inresponse to another preselected condition to vent the isolated controlfluid pressure, said relay means being responsive to the reducedmagnitude of the isolated control fluid pressure upon the ventingthereof to effect a corresponding proportional reduction in themagnitude of the applied fluid pressure.

3. A control valve for an anti-lock brake system comprising a housing,relay means movable in said housing and operable generally in responseto control fluid pressure subjected thereto to effect a meteredapplication through said housing of fluid pressure supplied thereto, andmeans for controlling the control fluid pressure selectively subjectedto said relay means including means for isolating the control fluidpressure acting on said relay means upon the occurrence of a preselectedcondition, and other means for venting the isolated control fluidpressure upon the occurrence of another preselected condition, saidrelay means being responsive to the reduced magnitude of the isolatedcontrol fluid pressure upon the venting thereof to effect acorresponding proportional reduction in the magnitude of the appliedfluid pressure, and a restricted flow passage in said housing for theflow therethrough of the control fluid pressure upon the subjectionthereof to said relay means, said included means and other meansdefining at least a portion of said restricted passage.

4. A control valve according to claim 3, comprising means in saidhousing including another flow passage connected across said restrictedflow passage in by-pass relation with said included means and said othermeans, the control fluid pressure acting on said relay means beingexhausted through said other flow passage in response to a fluidpressure differential established between the magnitudes of the controlfluid pressure acting on said relay means and that supplied to saidrestricted flow passage.

5. A control valve according to claim 4, wherein said last named meansalso includes uni-directional valve means for controlling said otherflow passage, said unidirectional valve means being normally urgedtoward a position closing said other flow passage and being movabletoward an open position effecting the exhaustion of the control fluidpressure acting on said relay means in response to the fluid pressuredifferential established there-across between the magnitudes of thecontrol fluid pressure acting on said relay means and that supplied tosaid restricted flow passage.

6. A control valve according to claim 2, wherein said first solenoidmeans also includes means for effecting venting of the isolated controlfluid pressure upon the isolation thereof.

7. A control valve according to claim 2, wherein said first solenoidmeans is energized in response to the first named preselected conditionto initially isolate the control fluid pressure acting on said relaymeans and there after effect venting of the isolated control fluidpressure.

8. A control valve according to claim 7, comprising a flow passage insaid housing for the flow therethrough of the control fluid pressureupon the subjection thereof to said relay means, said first solenoidmeans defining with said housing at least a portion of said flowpassage.

9. A control valve according to claim 8, comprising a first valve seatin said housing about said flow passage, and said first solenoid meanscomprising first valve means for engagement with said first valve seat,said first valve means being urged toward engagement with said firstvalve seat to close said flow passge and isolate the control fluidpressure acting on said relay means upon the energization of said firstnamed solenoid. means.

10. A control valve according to claim 9, comprising exhaust passagemeans in said housing and connected with said flow passage,a secondvalve seat in said housing about said exhaust passage means, said firstsolenoid means also comprising second valve means normally urged intoengagement with said second valve seat closing said exhaust passagemeans, said second valve means being urged toward a position disengagedfrom said second valve seat to open said exhaust passage means andeffect the venting of the isolated control fluid pressure upon theenergization of said first solenoid means.

11. A control valve according to claim 10, comprising other exhaustpassage means in said housing and connected with the control fluidpressure acting on said relay means, a third valve seat in said housingabout said other exhaust passage means, said other solenoid meansincluding third valve means normally urged into engagement with saidthird valve seat closing said other exhaust passage means, said thirdvalve means being urged toward a position disengaged from said thirdvalve seat to open said other exhaust passage means and effect furtherventing of the isolated control fluid pressure upon the energization ofsaid other solenoid means.

12. A control valve according to claim 11, wherein said relay meansdefines with said housing a control chamber connected with said flowpassage, other passage means in said housing connected between saidcontrol chamber and said flow passage in bypass relation therewith, thecontrol fluid pressure in said control chamber being exhausted throughsaid other passage means upon the exhaustion of the control fluidpressure subjected to said flow passage, a valve seat in said housingabout said other passage means, and valve means being normally engagedwith said valve seat to close said other passage means, said valve meansbeing urged toward a position disengaged from said valve seat to opensaid other passage means and effect the exhausting passage therethroughof the control fluid pressure in response to a fluid pressuredifferential established across said valve means between the magnitudesof the control fluid pressure in'said control chamber and that of theexhausting control fluid pressure subjected to said flow passage.

13. A control valve for an anti-lock brake system comprising a housing,relay means movable in said housing and defining therewith a controlchamber, said relay means being operable generally in response tocontrol fluid pressure in said chamber to effect the application andexhaustion of braking fluid pressure to and from said system, a controlport in said housing for connection with supplied and exhausting flowsof control fluid pressure, a flow passage in said housing connectedbetween said control port and chamber, a pair of solenoid means in saidhousing for energization upon the occurrence of a pair of preselectedconditions and defining at least portions of said restricted flowpassage including a pair of exhaust valve means in said restricted flowpassage and controlling the exhaustion of control fluid pressuretherethrough from said control chamber, respectively, and one of saidsolenoid means including other valve means controlling the passage ofthe control fluid pressure through said restricted flow passage andconnected for concerted movement with one of said exhaust valve means,said one solenoid means being energized upon the occurrence of one ofsaid preselected conditions to urge said other valve means and oneexhaust valve means toward positions in said restricted flow passageisolating the control fluid pressure in said control chamber from saidcontrol port and exhausting the isolated control fluid pressure fromsaid control chamber, respectively, and the other of said solenoid meansbeing thereafter energized upon the occurrence of the other of saidpreselected conditions to urge the other of said exhaust valve meanstoward a position in said restricted flow passage further exhausting theisolated control fluid pressure from said control chamber when said onesolenoid is energized.

14. A control valve according to claim 13, comprising passage means insaid housing connected between said control chamber and port in by-passrelation with said restricted flow passage, and check valve meanscontrolling said passage means, said check valve means being normallyurged toward a position closing said passage means and being movabletoward a position opening said passage means to permit exhausting flowtherethrough of the control fluid pressure from said control chamber inresponse to a pressure differential acting across said check valve meansbetween the magnitudes of the control fluid pressure in said controlchamber and the selective exhausting flow of the control fluid pressureat said control port.

15. A control valve according to claim 13, comprising a pair of exhaustpassages in said housing, said exhaust valve means being normally urgedtoward positions in said housing closing said exhaust passages and beingactuated toward positions in said housing opening said exhaust passagesto efiect the exhaustion of the isolated control fluid pressure upon theenergization of said solenoid means, respectively.

16. A control valve according to claim 15, wherein one of said exhaustpassages is predeterminately smaller than the other thereof.

17. A control valve according to claim 16, wherein said one exhaustpassage is connected with said restricted flow passage between saidother valve means and said control chamber, and the other of saidexhaust passages is connected with saidrestricted flow passage betweensaid one exhaust passage and said control chamber.

18. A control valve according to claim 16, comprising a pair of exhaustvalve seats on said housing about said exhaust passages for engagementwith said exhaust valve means, said exhaust valve means being normallyurged into engagement with said exhaust valve seats to close saidexhaust passages and being actuated toward positions disengaged fromsaid valve seats to effect the exhaustion of the isolated control fluidpressure upon energization of said solenoid means, respectively.

19. A control valve according to claim 18, wherein said one solenoidmeans includes a pole piece supported in said housing, other passagemeans extending through said pole piece and defining a portion of saidrestricted flow passage, winding means in said housing about said polepiece for excitation upon the occurrence of said one preselectedcondition, armature means movable in said one solenoid means upon theexcitation of said winding means, said armature means including said oneexhaust valve means and said other valve means, a third valve seat onsaid pole piece about said other passage means for engagement with saidother valve means, and spring means engaged with said armature meansnormally urging said one exhaust valve means into engagement with one ofsaid exhaust valve seats and said other valve means toward a positiondisengaged from said third valve seat, said armature being movableagainst said spring means in response to the excitation of said windingmeans toward a position engaging said other valve means with said thirdvalve seat to isolate the control fluid pressure in said control chamberand also disengaging said one exhaust valve means from said one exhaustvalve seat to open said one exhaust passage and effect the exhaustion ofthe isolated control fluid pressure therethrough.

20. A control valve according to claim 19, comprising an inlet port insaid housing adapted for connection with a source of braking fluidpressure, an outlet port in said housing adapted for connection with atleast one brake of said system, an exhaust port in said housing forconnection with said outlet port, fourth valve means movable in saidhousing and controlling pressure fluid communication between said inlet,outlet and exhaust ports, said relay means including a piston slidablein said housing and having opposed sides, one of said opposed sidesbeing subjected to the control fluid pressure in said control chamber,extension means on the other of the opposed sides of said piston havinga free end thereon for engagement with said fourth valve means, saidpiston being initially movable in response to the control fluid pressurein said control chamber acting on said one side thereof to engage saidfree end with said valve means interrupting pressure fluid communicationbetween said outlet and exhaust ports and being thereafter furthermovable to concertedly move said valve means toward a positionestablishing metered pressure fluid communication between said inlet andoutlet ports, the established fluid pressure at said outlet port actingon the other of the opposed sides of said'piston in opposition to thecontrol fluid pressure in said control chamber acting on said oneopposed side.

21. A control valve for an anti-lock brake system comprising a housing,relay means movable in said housing for, controlling said system anddefining with said housing a chamber for control fluid pressure, saidrelay means being operable generally in response to control fluidpressure in said chamber to effect a metered application and exhaustionof braking fluid pressure to and from said system, a control port insaid housing for selective connection with supplied and exhausting flowof control fluid pressure, a restricted passage in said housingconnected between said control port and chamber, a pair of solenoidmeans in said housing adapted for energization upon the occurrence ofdifferent preselected conditions in said system and defining with saidhousing at least portions of said rcstricted flow passage, one of saidsolenoid means including valve means movable in said restricted flowpassage and controlling the flow of control fluid pressure therethrough,said valve means being movable toward a position in said restricted flowpassage isolating the control fluid pressure in said chamber from thatat said control port upon the energization of said one solenoid means inresponse to the occurrence of one of said preselected conditions and theother of said solenoid means including other valve means movable in saidrestricted flow passage and controlling the exhaustion of control fluidpressure therefrom, said other valve means being movable toward aposition in said restricted flow passage exhausting isolated controlfluid pressure therethrough from said chamber upon the energization ofsaid other solenoid means in response to the occurrence of a differentpreselected condition only when said first named valve means is in itsisolating position.

22. A control valve according to claim 2, wherein said second solenoidmeans includes valve means movable toward a position to effect theventing of the isolated control fluid pressure upon the energization ofsaid second solenoid means.

23. A control valve according to claim 2, comprising exhaust passagemeans in said housing and subjected to the isolated control fluidpressure, said second solenoid means normally closing said exhaustpassage means.

24. A control valve according to claim 23, comprising a valve seat insaid housing about said exhaust passage means, and said second solenoidmeans including valve means for engagement with said valve seat, saidvalve means being normally urged into engagement with said valve seat toclose said exhaust passage means and said valve means being movabletoward a position disengaged from said valve seat to open said exhaustpassage means effecting the venting of the isolated control fluidpressure therethrough upon the energization of said second solenoidmeans.

25. A control valve according to claim 2, comprising exhaust passagemeans in said housing for communication with the isolated control fluidpressure, said first solenoid means normally closing said exhaustpassage means.

26. A control valve according to claim 25, comprising a valve seat insaid housing about said exhaust passage means, and said first solenoidmeans including valve means for engagement with said valve seat, saidvalve means being normally urged into engagement with said valve seatand being movable toward a position disengaged from said valve seat uponthe energization of said first solenoid means.

27. A control valve according to claim 2, comprising first and secondexhaust passage means in said housing for communication with theisolated control fluid pressure, first and second valve seats in saidhousing about said first and second exhaust passage means, said firstand second solenoid means including first and second valve means engagedwith said first and second valve seats to close said first and secondexhaust passage means, and said first and second valve means beingmovable toward positions disengaged from said first and second valveseats upon the energization of said first and second solenoid means,respectively.

28. A control valve according to claim 27, comprising a flow passage insaid housing for the flow therethrough of the control fluid pressureupon the subjection thereof to said relay means, a third valve seat insaid housing about saidflow passage, and third valve means on said firstsolenoid means for engagement with said third valve seat, said thirdvalve means being movable into engagement with said third valve seat toisolate the control fluid pressure acting on said relay means.

29. A control valve according to claim '8, wherein passage means uponthe energization of said solenoid valve to engage said first named valvemeans with said first named valve seat.

36. A control valve for an anti-lock brake system comprising a housinghaving a control port therein, relay means movable in said housing anddefining therewith a control chamber connected with said control port,said relay means being operable generally in said flow passage isrestricted to predeterminately re- 1 ing flow of the isolated controlfluid pressure there-' through, respectively.

31. A control valve according to claim 30, wherein one of said firstnamed and other exhaust passage means is more restricted than the otherthereof so that the rate of venting vflow of the isolated control fluidpressure through said one of said first named and other exhaust passagemeans is predeterminately less than that through the other of said firstnamed and other exhaust passage means.

32. A control valve according to claim 1, comprising exhaust passagemeans in said housing for communication with the isolated control fluidpressure, said solenoid valve normally closing said exhaust passagemeans.

33. A control valve according to claim 32', comprising a valve seat insaid housing about said exhaust passage means, and said solenoid valveincluding valve means normally engaged with said valve seat to closesaid exhaust passage means and said valve means being movable toward aposition disengaged from said valve seat to open said exhaust passagemeans venting the isolated control fluid pressure therethrough upon theenergization of said solenoid valve.

34. A control valve according to claim 1, comprisinga flow passage insaid housing for the flow therethrough of the control fluid pressureupon the subjection thereof to said relay means, a valve seat in saidhousing said other valve means being movable toward a posi-- tiondisengaged from said other valve seat to vent th isolated control fluidpressure through said exhaust response to control fluid pressure in saidcontrol chamber to effect the application through said housing ofbraking fluid pressure to said system, an exhaust port in said housingand connected with said control chamber, and an electric solenoid valveenergized in response to a preselected condition for controllingpressure fluid communication between said control port and said controlchamber and between said exhaust port and said control chamber, saidsolenoid valve being responsive to the occurrence of the preselectedcondition to interrupt pressure fluid communication between said controlport and control chamber isolating the control fluid pressure thereinacting on said relay means and also to establish pressure fluidcommunication between said exhaust port and said control chamber ventingthe isolated control fluid pressure in said chamber.

37. A control valve according to claim 36, comprising first and secondvalve seats in said housing between said control port and controlchamber and between said exhaust port and control chamber, respectively,

said solenoid valve including valve means normally enother preselectedcondition for controlling pressure. fluid communication between saidother exhaust port and chamber, said other solenoid valve beingenergized upon the occurrence of the other preselected condition toalsoestablish pressure fluid communication between said other exhaustport and said control chamber venting'the isolated control fluidpressure in said chamber.

39. A control valve according to claim 38, comprising a third valve seatin said housing between said control chamber and said other exhaustports, and said other solenoid valve including otherv valve meansnormally engaged with said third valve seat, said other valve meansbeing movable toward a position disengaged from said third valve seat toestablish the pressure fluid communication between said other exhaustport and said control chamber venting the isolated control fluidpressure in said control chamber upon the energization of said othersolenoid valve.

' t i i i t UNITED STATES PATENT @FFICE (IERTIFIQAT F QQRRECTION PatentNo. 3,758,167 Dated $e ptember 1.1., 1973 Inventor(s) John A. Machek Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 5, line 4, after pres smz'e" insert 0 Upon such rapid exhaustionof the control fluid pressure 0 Column 6, line 1 "th" should read theColumn 7, line 39, '194" should read 100 "u, Column 9, line 43, -ll"-should Signed and sealed this 9th day of April 197t (SEAL) Attest:

MARSHALL DA'NN EDWARD l 'iaFLETOtfialRfli-t.

Commissioner of Patents Attesting Officer USCOMM-DC 60376-P69 FORMPC4050 (10-69) us. GOVERNMENT PRINTING OFFICE: I969 0-366-334.

1. A control valve for an anti-lock brake system comprising a housing,relay means movable in said housing and operable generally in responseto control fluid pressure subjected thereto to effect a meteredapplication through said housing of fluid pressure supplied thereto, andmeans for controlling the control fluid pressure subjected to said relaymeans comprising an electric solenoid valve energized in response to apreselected condition to isolate the control fluid pressure acting onsaid relay means and vent the isolated control fluid pressure, saidrelay means being responsive to the reduction of the control fluidpressure upon the venting thereof to effect a proportional reduction ofthe applied fluid pressure.
 2. A control valve for an anti-lock brakesystem comprising a housing, relay means movable in said housing andoperable generally in response to control fluid pressure subjectedthereto to effect a metered application through said housing of fluidpressure supplied thereto, and means for controlling the control fluidpressure subjected to said relay means comprising a first electricsolenoid means energized in response to a preselected condition toisolate the control fluid pressure acting on said relay means, and asecond electric solenoid means energized in response to anotherpreselected condition to vent the isolated control fluid pressure, saidrelay means being responsive to the reduced magnitude of the isolatedcontrol fluid pressure upon the venting thereof to effect acorresponding proportional reduction in the magnitude of the appliedfluid pressure.
 3. A control valve for an anti-lock brake systemcomprising a housing, relay means movable in said housing and operablegenerally in response to control fluid pressure subjected thereto toeffect a metered application through said housing of fluid pressuresupplied thereto, and means for controlling the control fluid pressureselectively subjected to said relay means including means for isolatingthe control fluid pressure acting on said relay means upon theoccurrence of a preselected condition, and other means for venting theisolated control fluid pressure upon the occurrence of anotherpreselected condition, said relay means being responsive to the reducedmagnitude of the isolated control fluid pressure upon the ventingthereof to effect a corresponding proportional reduction in themagnitude of the applied fluid pressure, and a restricted flow passagein said housing for the flow therethrough of the control fluid pressureupon the subjection thereof to said relay means, said included means andother means defining at least a portion of said restricted passage.
 4. Acontrol valve according to claim 3, comprising means in said housingincluding another flow passage connected across said restricted flowpassage in by-pass relation with said included means and said othermeans, the control fluid pressure acting on said relay means beingexhausted through said other flow passage in response to a fluidpressure differential established between the magnitudes of the controlfluid pressure acting on said relay means and that supplied to saidrestricted flow passage.
 5. A control valve according to claim 4,wherein said last named means also includes uni-dirEctional valve meansfor controlling said other flow passage, said unidirectional valve meansbeing normally urged toward a position closing said other flow passageand being movable toward an open position effecting the exhaustion ofthe control fluid pressure acting on said relay means in response to thefluid pressure differential established there-across between themagnitudes of the control fluid pressure acting on said relay means andthat supplied to said restricted flow passage.
 6. A control valveaccording to claim 2, wherein said first solenoid means also includesmeans for effecting venting of the isolated control fluid pressure uponthe isolation thereof.
 7. A control valve according to claim 2, whereinsaid first solenoid means is energized in response to the first namedpreselected condition to initially isolate the control fluid pressureacting on said relay means and thereafter effect venting of the isolatedcontrol fluid pressure.
 8. A control valve according to claim 7,comprising a flow passage in said housing for the flow therethrough ofthe control fluid pressure upon the subjection thereof to said relaymeans, said first solenoid means defining with said housing at least aportion of said flow passage.
 9. A control valve according to claim 8,comprising a first valve seat in said housing about said flow passage,and said first solenoid means comprising first valve means forengagement with said first valve seat, said first valve means beingurged toward engagement with said first valve seat to close said flowpassge and isolate the control fluid pressure acting on said relay meansupon the energization of said first named solenoid means.
 10. A controlvalve according to claim 9, comprising exhaust passage means in saidhousing and connected with said flow passage, a second valve seat insaid housing about said exhaust passage means, said first solenoid meansalso comprising second valve means normally urged into engagement withsaid second valve seat closing said exhaust passage means, said secondvalve means being urged toward a position disengaged from said secondvalve seat to open said exhaust passage means and effect the venting ofthe isolated control fluid pressure upon the energization of said firstsolenoid means.
 11. A control valve according to claim 10, comprisingother exhaust passage means in said housing and connected with thecontrol fluid pressure acting on said relay means, a third valve seat insaid housing about said other exhaust passage means, said other solenoidmeans including third valve means normally urged into engagement withsaid third valve seat closing said other exhaust passage means, saidthird valve means being urged toward a position disengaged from saidthird valve seat to open said other exhaust passage means and effectfurther venting of the isolated control fluid pressure upon theenergization of said other solenoid means.
 12. A control valve accordingto claim 11, wherein said relay means defines with said housing acontrol chamber connected with said flow passage, other passage means insaid housing connected between said control chamber and said flowpassage in bypass relation therewith, the control fluid pressure in saidcontrol chamber being exhausted through said other passage means uponthe exhaustion of the control fluid pressure subjected to said flowpassage, a valve seat in said housing about said other passage means,and valve means being normally engaged with said valve seat to closesaid other passage means, said valve means being urged toward a positiondisengaged from said valve seat to open said other passage means andeffect the exhausting passage therethrough of the control fluid pressurein response to a fluid pressure differential established across saidvalve means between the magnitudes of the control fluid pressure in saidcontrol chamber and that of the exhausting control fluid pressuresubjected to said flow passage.
 13. A control valve for an anti-lockbrake systeM comprising a housing, relay means movable in said housingand defining therewith a control chamber, said relay means beingoperable generally in response to control fluid pressure in said chamberto effect the application and exhaustion of braking fluid pressure toand from said system, a control port in said housing for connection withsupplied and exhausting flows of control fluid pressure, a flow passagein said housing connected between said control port and chamber, a pairof solenoid means in said housing for energization upon the occurrenceof a pair of preselected conditions and defining at least portions ofsaid restricted flow passage including a pair of exhaust valve means insaid restricted flow passage and controlling the exhaustion of controlfluid pressure therethrough from said control chamber, respectively, andone of said solenoid means including other valve means controlling thepassage of the control fluid pressure through said restricted flowpassage and connected for concerted movement with one of said exhaustvalve means, said one solenoid means being energized upon the occurrenceof one of said preselected conditions to urge said other valve means andone exhaust valve means toward positions in said restricted flow passageisolating the control fluid pressure in said control chamber from saidcontrol port and exhausting the isolated control fluid pressure fromsaid control chamber, respectively, and the other of said solenoid meansbeing thereafter energized upon the occurrence of the other of saidpreselected conditions to urge the other of said exhaust valve meanstoward a position in said restricted flow passage further exhausting theisolated control fluid pressure from said control chamber when said onesolenoid is energized.
 14. A control valve according to claim 13,comprising passage means in said housing connected between said controlchamber and port in by-pass relation with said restricted flow passage,and check valve means controlling said passage means, said check valvemeans being normally urged toward a position closing said passage meansand being movable toward a position opening said passage means to permitexhausting flow therethrough of the control fluid pressure from saidcontrol chamber in response to a pressure differential acting acrosssaid check valve means between the magnitudes of the control fluidpressure in said control chamber and the selective exhausting flow ofthe control fluid pressure at said control port.
 15. A control valveaccording to claim 13, comprising a pair of exhaust passages in saidhousing, said exhaust valve means being normally urged toward positionsin said housing closing said exhaust passages and being actuated towardpositions in said housing opening said exhaust passages to effect theexhaustion of the isolated control fluid pressure upon the energizationof said solenoid means, respectively.
 16. A control valve according toclaim 15, wherein one of said exhaust passages is predeterminatelysmaller than the other thereof.
 17. A control valve according to claim16, wherein said one exhaust passage is connected with said restrictedflow passage between said other valve means and said control chamber,and the other of said exhaust passages is connected with said restrictedflow passage between said one exhaust passage and said control chamber.18. A control valve according to claim 16, comprising a pair of exhaustvalve seats on said housing about said exhaust passages for engagementwith said exhaust valve means, said exhaust valve means being normallyurged into engagement with said exhaust valve seats to close saidexhaust passages and being actuated toward positions disengaged fromsaid valve seats to effect the exhaustion of the isolated control fluidpressure upon energization of said solenoid means, respectively.
 19. Acontrol valve according to claim 18, wherein said one solenoid meansincludes a pole piece supported in said housing, other passage meansextending through said pole piece and defining a portion of saidrestricted flow passage, winding means in said housing about said polepiece for excitation upon the occurrence of said one preselectedcondition, armature means movable in said one solenoid means upon theexcitation of said winding means, said armature means including said oneexhaust valve means and said other valve means, a third valve seat onsaid pole piece about said other passage means for engagement with saidother valve means, and spring means engaged with said armature meansnormally urging said one exhaust valve means into engagement with one ofsaid exhaust valve seats and said other valve means toward a positiondisengaged from said third valve seat, said armature being movableagainst said spring means in response to the excitation of said windingmeans toward a position engaging said other valve means with said thirdvalve seat to isolate the control fluid pressure in said control chamberand also disengaging said one exhaust valve means from said one exhaustvalve seat to open said one exhaust passage and effect the exhaustion ofthe isolated control fluid pressure therethrough.
 20. A control valveaccording to claim 19, comprising an inlet port in said housing adaptedfor connection with a source of braking fluid pressure, an outlet portin said housing adapted for connection with at least one brake of saidsystem, an exhaust port in said housing for connection with said outletport, fourth valve means movable in said housing and controllingpressure fluid communication between said inlet, outlet and exhaustports, said relay means including a piston slidable in said housing andhaving opposed sides, one of said opposed sides being subjected to thecontrol fluid pressure in said control chamber, extension means on theother of the opposed sides of said piston having a free end thereon forengagement with said fourth valve means, said piston being initiallymovable in response to the control fluid pressure in said controlchamber acting on said one side thereof to engage said free end withsaid valve means interrupting pressure fluid communication between saidoutlet and exhaust ports and being thereafter further movable toconcertedly move said valve means toward a position establishing meteredpressure fluid communication between said inlet and outlet ports, theestablished fluid pressure at said outlet port acting on the other ofthe opposed sides of said piston in opposition to the control fluidpressure in said control chamber acting on said one opposed side.
 21. Acontrol valve for an anti-lock brake system comprising a housing, relaymeans movable in said housing for controlling said system and definingwith said housing a chamber for control fluid pressure, said relay meansbeing operable generally in response to control fluid pressure in saidchamber to effect a metered application and exhaustion of braking fluidpressure to and from said system, a control port in said housing forselective connection with supplied and exhausting flow of control fluidpressure, a restricted passage in said housing connected between saidcontrol port and chamber, a pair of solenoid means in said housingadapted for energization upon the occurrence of different preselectedconditions in said system and defining with said housing at leastportions of said restricted flow passage, one of said solenoid meansincluding valve means movable in said restricted flow passage andcontrolling the flow of control fluid pressure therethrough, said valvemeans being movable toward a position in said restricted flow passageisolating the control fluid pressure in said chamber from that at saidcontrol port upon the energization of said one solenoid means inresponse to the occurrence of one of said preselected conditions and theother of said solenoid means including other valve means movable in saidrestricted flow passage and controlling the exhaustion of control fluidpressure therefrom, said other valve means being movable toward apOsition in said restricted flow passage exhausting isolated controlfluid pressure therethrough from said chamber upon the energization ofsaid other solenoid means in response to the occurrence of a differentpreselected condition only when said first named valve means is in itsisolating position.
 22. A control valve according to claim 2, whereinsaid second solenoid means includes valve means movable toward aposition to effect the venting of the isolated control fluid pressureupon the energization of said second solenoid means.
 23. A control valveaccording to claim 2, comprising exhaust passage means in said housingand subjected to the isolated control fluid pressure, said secondsolenoid means normally closing said exhaust passage means.
 24. Acontrol valve according to claim 23, comprising a valve seat in saidhousing about said exhaust passage means, and said second solenoid meansincluding valve means for engagement with said valve seat, said valvemeans being normally urged into engagement with said valve seat to closesaid exhaust passage means and said valve means being movable toward aposition disengaged from said valve seat to open said exhaust passagemeans effecting the venting of the isolated control fluid pressuretherethrough upon the energization of said second solenoid means.
 25. Acontrol valve according to claim 2, comprising exhaust passage means insaid housing for communication with the isolated control fluid pressure,said first solenoid means normally closing said exhaust passage means.26. A control valve according to claim 25, comprising a valve seat insaid housing about said exhaust passage means, and said first solenoidmeans including valve means for engagement with said valve seat, saidvalve means being normally urged into engagement with said valve seatand being movable toward a position disengaged from said valve seat uponthe energization of said first solenoid means.
 27. A control valveaccording to claim 2, comprising first and second exhaust passage meansin said housing for communication with the isolated control fluidpressure, first and second valve seats in said housing about said firstand second exhaust passage means, said first and second solenoid meansincluding first and second valve means engaged with said first andsecond valve seats to close said first and second exhaust passage means,and said first and second valve means being movable toward positionsdisengaged from said first and second valve seats upon the energizationof said first and second solenoid means, respectively.
 28. A controlvalve according to claim 27, comprising a flow passage in said housingfor the flow therethrough of the control fluid pressure upon thesubjection thereof to said relay means, a third valve seat in saidhousing about said flow passage, and third valve means on said firstsolenoid means for engagement with said third valve seat, said thirdvalve means being movable into engagement with said third valve seat toisolate the control fluid pressure acting on said relay means.
 29. Acontrol valve according to claim 8, wherein said flow passage isrestricted to predeterminately reduce the rate of flow of said controlfluid pressure therethrough.
 30. A control valve according to claim 11,wherein said first named and other exhaust passage means are restrictedto predeterminately reduce the rate of venting flow of the isolatedcontrol fluid pressure therethrough, respectively.
 31. A control valveaccording to claim 30, wherein one of said first named and other exhaustpassage means is more restricted than the other thereof so that the rateof venting flow of the isolated control fluid pressure through said oneof said first named and other exhaust passage means is predeterminatelyless than that through the other of said first named and other exhaustpassage means.
 32. A control valve according to claim 1, comprisingexhaust passage means in said housing for communication with theisolated control flUid pressure, said solenoid valve normally closingsaid exhaust passage means.
 33. A control valve according to claim 32,comprising a valve seat in said housing about said exhaust passagemeans, and said solenoid valve including valve means normally engagedwith said valve seat to close said exhaust passage means and said valvemeans being movable toward a position disengaged from said valve seat toopen said exhaust passage means venting the isolated control fluidpressure therethrough upon the energization of said solenoid valve. 34.A control valve according to claim 1, comprising a flow passage in saidhousing for the flow therethrough of the control fluid pressure upon thesubjection thereof to said relay means, a valve seat in said housingabout said flow passage, said solenoid valve including valve means forengagement with said valve seat, said valve means being movable intoengagement with said valve seat to close said flow passage and isolatethe control fluid pressure acting on said relay means upon theenergization of said solenoid valve.
 35. A control valve according toclaim 34, comprising exhaust passage means in said housing forcommunication with the isolated control fluid pressure, another valveseat in said housing about said exhaust passage means, and said solenoidvalve including other valve means for engagement with said other valveseat, said other valve means being movable toward a position disengagedfrom said other valve seat to vent th isolated control fluid pressurethrough said exhaust passage means upon the energization of saidsolenoid valve to engage said first named valve means with said firstnamed valve seat.
 36. A control valve for an anti-lock brake systemcomprising a housing having a control port therein, relay means movablein said housing and defining therewith a control chamber connected withsaid control port, said relay means being operable generally in responseto control fluid pressure in said control chamber to effect theapplication through said housing of braking fluid pressure to saidsystem, an exhaust port in said housing and connected with said controlchamber, and an electric solenoid valve energized in response to apreselected condition for controlling pressure fluid communicationbetween said control port and said control chamber and between saidexhaust port and said control chamber, said solenoid valve beingresponsive to the occurrence of the preselected condition to interruptpressure fluid communication between said control port and controlchamber isolating the control fluid pressure therein acting on saidrelay means and also to establish pressure fluid communication betweensaid exhaust port and said control chamber venting the isolated controlfluid pressure in said chamber.
 37. A control valve according to claim36, comprising first and second valve seats in said housing between saidcontrol port and control chamber and between said exhaust port andcontrol chamber, respectively, said solenoid valve including valve meansnormally engaged with said second valve seat and disengaged from saidfirst valve seat, said valve means being movable toward a positionengaged with said first valve seat isolating the control fluid pressurein said control chamber and toward a position disengaged from saidsecond valve seat to vent the isolated control fluid pressure in saidcontrol chamber to said exhaust port.
 38. A control valve according toclaim 36, comprising another exhaust port in said housing and connectedwith said control chamber, and another electric solenoid valve in saidhousing energized in response to another preselected condition forcontrolling pressure fluid communication between said other exhaust portand chamber, said other solenoid valve being energized upon theoccurrence of the other preselected condition to also establish pressurefluid communication between said other exhaust port and said controlchamber venting the isolated control fluid pressure in said chamber. 39.A control valve according to claim 38, comprising a third valve seat insaid housing between said control chamber and said other exhaust ports,and said other solenoid valve including other valve means normallyengaged with said third valve seat, said other valve means being movabletoward a position disengaged from said third valve seat to establish thepressure fluid communication between said other exhaust port and saidcontrol chamber venting the isolated control fluid pressure in saidcontrol chamber upon the energization of said other solenoid valve.